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/* Copyright (c) 2018 The Tor Project, Inc. */
/* See LICENSE for licensing information */
/**
* \file ctassert.h
*
* \brief Compile-time assertions: CTASSERT(expression).
*/
#ifndef TOR_CTASSERT_H
#define TOR_CTASSERT_H
#include "lib/cc/compat_compiler.h"
/**
* CTASSERT(expression)
*
* Trigger a compiler error if expression is false.
*/
#if __STDC_VERSION__ >= 201112L
/* If C11 is available, just use _Static_assert. */
#define CTASSERT(x) _Static_assert((x), #x)
#else /* !(__STDC_VERSION__ >= 201112L) */
/*
* If C11 is not available, expand __COUNTER__, or __INCLUDE_LEVEL__
* and __LINE__, or just __LINE__, with an intermediate preprocessor
* macro CTASSERT_EXPN, and then use CTASSERT_DECL to paste the
* expansions together into a unique name.
*
* We use this name as a typedef of an array type with a positive
* length if the assertion is true, and a negative length of the
* assertion is false, which is invalid and hence triggers a compiler
* error.
*/
#if defined(__COUNTER__)
#define CTASSERT(x) CTASSERT_EXPN((x), c, __COUNTER__)
#elif defined(__INCLUDE_LEVEL__)
#define CTASSERT(x) CTASSERT_EXPN((x), __INCLUDE_LEVEL__, __LINE__)
#else
/* hope it's unique enough */
#define CTASSERT(x) CTASSERT_EXPN((x), l, __LINE__)
#endif /* defined(__COUNTER__) || ... */
#define CTASSERT_EXPN(x, a, b) CTASSERT_DECL(x, a, b)
#define CTASSERT_DECL(x, a, b) \
typedef char tor_ctassert_##a##_##b[(x) ? 1 : -1] ATTR_UNUSED; EAT_SEMICOLON
#endif /* __STDC_VERSION__ >= 201112L */
#endif /* !defined(TOR_CTASSERT_H) */
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